1. Field of the Invention
This invention relates generally to a method and apparatus for treating chondromalacia, and more particularly to a method and apparatus that treats chondromalacia with minimal disruption of the cartilage bed of the knee.
This invention also relates generally to thermal therapy techniques for treating joint pathologies arthroscopically. More specifically, techniques to manipulate the thermal dynamic aspects of the joint capsule environment as approached arthroscopically.
2. Description of Related Art
The normal function of joints in humans depends on the distribution of relatively large forces across the body surfaces. In diarthrodial joints the magnitude of the joint forces reaches levels four to seven times body weight. These forces applied to joints are dispersed by articular cartilage. Cartilage function occurs via a highly organized extracellular matrix maintaining a fixed charge density and possessing a high affinity for water.
Normal articular cartilage consists of an assembly of large and small proteoglycans, collagens, hyaluronic acid and glycoproteins. These matrix macromolecules originate from chondrocytes localized in a nonrandom pattern through the cartilage matrix. In normal joints, chondrocytes do not proliferate; dividing chondrocytes indicate-a change in cartilage homeostasis, either as regeneration or attempted repair.
Chondromalacia occurs when cartilage beds in joints become worn and strands of cartilage distended away from their respective cartilage beds and extend into the joint capsule. The cartilage surface becomes visibly disrupted, fissured and fibrillated. This has deterious effects on the mechanical properties of articular cartilage. This distension has been associated with knee pain. Treatment to date has included surgical intervention. In one arthroscopic procedure, a shaver is introduced through an arthroscope and is used to remove the strands of disrupted and fibrillated cartilage. However, this treatment can disrupt and remove part of the normal cartilage bed and does not restore a smooth surface nor the mechanical function.
It would be desirable to provide a method and apparatus treating fibrillated cartilage joint surfaces or irregular cartilage joint surfaces by delivering sufficient thermal energy to reduce a level of fibrillation or irregularity of the fibrillated cartilage joint surface or the irregular cartilage joint surface. It would also be desirable to modify the fibrillated cartilage surface to a smooth surface. It would be further desirable to treat chondromalacia by reducing a level of fibrillation or irregularity of a fibrillated or irregular cartilage joint surface.
Arthroscopic interventions include a variety of modalities in the treatment of various joint pathologies. These modalities include mechanical shavers, electrosurgical devices, mechanical burrs and drills and electrothermal interventions for the modification of collagenous structures. Heat may be generated by mechanical means as a byproduct of friction, or by ohmic (resistive) heating as a result of electromagnetic currents passing through tissues generating heat. In certain instances, thermal insult of the adjacent structures can have significant implications and must be minimized to the maximum extent possible. The inadvertent exposure to these adjacent tissues can result in the loss of important viable cells not intended for destruction, such as articular cartilage, subchondral bone and neurovascular structures that may reside in close proximity to structures intended for these therapies. One such instance is in the treatment of chondromalacia by electrothermal coagulation of the fibrillated cartilage surface.
Chondromalacia is a condition of the articular cartilage, particularly the knee that is addressed using thermal techniques. Conventional treatment for chondromalacia involves debridement by mechanically cutting or shaving of any non-viable or troublesome tissues at the time of arthroscopic surgery. This condition has also been approached with lasers and conventional electrosurgery devices.
One apparatus and method as described in parent application U.S. Ser. No. 08/700,196, filed Aug. 20, 1996, now pending, describes treating the fibrillated cartilage surflces by utilizing the properties of the collage component of the articular cartilage. These properties allow the doctor to treat chondromalacia or other chondral defects with thermal energy at levels that coagulate the fibrillated or non-intact cartilage tissue, sealing the articular cartilage structures thereof, thereby inhibiting further degradation of the cartilage matrix. The mechanical aspects of the knee joint are thus maintained with little change in articular function.
Thermal chondroplasty utilizing a temperature feedback system has several advantages over the mechanical shaving method. With debridement and mechanical shaving, inadvertent disruption of healthy viable articular cartilage is practically unavoidable and further results in dysfunction of the joint. Further, the resultant surface architecture of the haline cartilage remains discarded whereby remaining articular cartilage strands are still present in the joint area and bits of fibrillated cartilage continue to serve as a source of joint inflammation and pain.
The thermal treatment approach provides both a smooth gliding surface for the corresponding arcticular surfaces and coagulates and seals the fibrillated strands. The fibrillated strands would otherwise break off as a result of further degeneration and mechanical wear due to the pressure of weight bearing and movement during joint articulation. These remnants of cartilage irritate the joint, in particular the synovial lining, which became inflamed from contact with these free floating pieces of tissue and the chemical components that are a byproduct of the breakdown of these tissues.
Concerns related to the use of thermal energy in close proximity to healthy and viable tissues (i.e., non-targeted tissues) include the potential for thermal collateral damage or injury to tissues not intended for removal or treatment. The thermal effect on non-targeted tissues is compounded by the articular cartilage natural characteristic of not having the ability to repair itself or regenerate as with other types of tissue. Thus, temperature feedback control devices and methods limit, but do not all together eliminate these potential adverse effects.
For these reasons, it would be desirable to provide an approach to reducing this type of collateral damage and further limit and reduce the potential for extraneous and collateral thermal exposure of non-targeted tissue. Such an approach should be able to treat targeted cartilage surfaces and other structures found in the arthroscopic setting in conjunction with thermal therapy procedures, and to simultaneously protect healthy and viable non-targeted tissues that are in close proximity to, or are continuous with, tissues targeted for thermal treatment. Such an approach should allow, for example, the treatment of damaged articular cartilage with minimal or no injury to the underlying viable cartilage and subehondral bone or other structures in the diarthrodial joint.
Accordingly, an object of the invention is to provide a method and apparatus for treating fibrillated or irregular cartilage joint surfaces.
Another object of the invention is to provide a method and apparatus for delivering sufficient thermal energy to reduce a level of fibrillation of a fibrillated cartilage joint surface.
Yet another object of the invention is to provide a method and apparatus for delivering sufficient thermal energy to modify a fibrillated cartilage joint surface to a smooth surface.
A further object of the invention is to provide a method and apparatus for delivering sufficient thermal energy to modify an irregular cartilage joint surface to a smoother surface.
Still a further object of the invention is to provide a method and apparatus for delivering sufficient thermal energy to at least a portion of a plurality of cartilage strands coupled to a fibrillated cartilage surface, and melt the strands onto the fibrillated cartilage surface.
Another object of the invention is to provide a method and apparatus that uses thermal energy to treat chondromalacia.
These and other objects of the invention are achieved in a thermal energy delivery apparatus that has a probe means including a distal end and a proximal end. A first electrode means is positioned at the distal end of the probe means. The first electrode means is configured to deliver sufficient thermal energy to a fibrillated cartilage surface to reduce a level of fibrillation of the fibrillated cartilage surface. A cabling means is coupled to the proximal end of the probe means.
In one embodiment of the invention, an apparatus is configured to be positioned adjacent to a fibrillated cartilage joint surface. A probe means has a distal end and a proximal end. An insulator means has a first surface and a second surface. A first electrode means is positioned on the first surface of the insulator. The first electrode means has a first thermal energy delivery surface configured to deliver sufficient thermal energy to a plurality of cartilage strands coupled to the fibrillated cartilage joint surface to reduce a level of fibrillation of surface. A second electrode means is positioned on the second surface of the insulator. A cable means is coupled to the proximal end of the probe means.
In another embodiment, a method modifies a geometry of a fibrillated cartilage surface. A thermal energy delivery device is provided and includes a probe means with a distal end and a thermal energy delivery surface. A thermal energy source is also provided and coupled to the thermal energy delivery surface. The thermal energy delivery surface is positioned adjacent to the fibrillated cartilage surface in a non-contacting position. Sufficient thermal energy is delivered from the thermal energy delivery surface to reduce a level of fibrillation of the fibrillated cartilage surface.
The method and apparatus of the present invention can also be used to decrease the level of irregularity of an irregular cartilage surface.
The apparatus of the present invention may also include a sensor means positioned at the distal end of the probe means. A comparator means is provided and compares a measured temperature value at the sensor means with a predetermined temperature value. The comparator means generates a disabling signal if the measured temperature value exceeds the predetermined maximum temperature value. A communication means is provided and communicates the disabling signal to the thermal energy source means to cease further delivery of energy from the thermal energy source means to the first electrode means.
In various embodiments of the invention, sufficient thermal energy is delivered from the thermal energy delivery surface to modify the fibrillated cartilage surface to a smooth surface. Thermal energy is delivered from the thermal energy delivery surface to create a less fibrillated, fibrillated cartilage surface. Thermal energy is delivered from the thermal energy delivery surface to cause at least a portion of a plurality of cartilage strands coupled to the fibrillated cartilage surface to create a smoothened cartilage surface. Thermal energy is delivered from the thermal energy delivery surface to cause at least a portion of a plurality of cartilage strands coupled to the fibrillated cartilage surface to melt onto the fibrillated cartilage surface. At least a portion of a plurality of cartilage strands are melted to create a smoothened cartilage surface.
A method according the invention includes the pre-cooling of tissue by means of an irrigating solution cooled to a very low temperature. The cooled solution is used to Lavage the joint for a period of time prior to the application of thermal therapeutic energy. It will be appreciated that such low temperatures decrease the temperature of the associated structures exposed within the field of the synovial cavity, thus providing a conventive thermal offset that will limit any temperature rise in response to any thermal energy applied to the tissue. The presence of the lower offset temperature protects the non-targeted tissue from collateral damage as a result of the thermal treatment.
A further understanding of the nature and advantages of the present invention will become apparent by reference to the following specification and drawings.